Objective:

Background:

Transthyretin (ATTR) amyloidosis is a rare disease with heterogenous clinical presentation. This heterogeneity introduces challenges in the measurement of health-related quality of life. The ATTR-QOL is a disease-specific, patient-reported outcome measure developed to capture the symptoms and impacts from patients across all types of ATTR amyloidosis (i.e., hereditary and wild-type). 

Design/Methods:

Adult patients with symptomatic ATTR amyloidosis in the United States completed the ATTR-QOL at 2 timepoints, along with additional surveys which served as criterion measures. Factor analyses and tests of differential item functioning (DIF) were conducted to confirm a hypothesized domain structure and identify redundant items. A scoring algorithm was proposed and tested. Psychometric analyses included tests of internal consistency reliability, test-retest reliability, convergent validity, and known-groups validity.

Results:

The analytic sample included 233 participants. Factor analysis and tests of DIF identified redundant items and supported the formation of 4 impact domains: Daily Activities, Social/Role Functioning, Emotional Wellbeing, and Physical Functioning. Results were confirmed with a secondary dataset. The proposed scoring algorithm was refined. Twelve impact items were dropped from the ATTR-QOLv2 as a result of factor and DIF analyses. Results supported the internal consistency reliability, test-retest reliability, convergent validity, and known-groups validity of the ATTR-QOL Impact scales. Patients with worse symptom severity, cardiac functioning, or unemployment due to ATTR amyloidosis had worse ATTR-QOL Impact scale scores. 

Conclusions:

Findings support the use of the 4 ATTR-QOL Impact scales in patients with ATTR amyloidosis. This study resulted in updates to the ATTR-QOL for item reduction and the development of a scoring algorithm. Future work will be conducted in a clinical setting to explore responsiveness and establish meaningful within-patient change thresholds.